Control mechanism



Nov. 24, 1936. w. H. KNISKERN 2,062,095

CONTROL MECHANI SM 3 Sheets-Sheet 1 Filed Oct. 10, 1930 INVENTOR l Va/fer Amkfi rn ATTORNEY Nov. 24, 1936.

W. H. KNISKERN CONTROL MECHANISM Filed Oct. 10, 1930 3 Sheets-Shee t 2 INVENTOR ATTORNEY Nov. 24, 1936. w. H. KNISKERN CONTROL MECHANISM Filed Oct. 10, 1930 3 Sheets-Sheet 3 INVENTOR Wa/fer W Z/Jfiern B g ATTORNEY Patented Nov. 24, 1936 2,062,095

UNITED STATES PATENT OFFICE CONTROL MECHANISM Walter H. Kniskern, Prince George County, Va., assignor to Atmospheric Nitrogen Corporation, New York, N. Y., a corporation of New York Application October 10, 1930, Serial No. 487,887

12 Claims. (01. 137-68) This invention relates to control apparatus level to the predetermined height by diminishing and more particularly to control apparatus for the discharge opening and thus diminishing the maintaining a substantially constant level of volume of liquid discharged when, due to increase liquid in a vessel into and from which liquid is n p ssure decrease in V s y, density 5 introduced and discharged. The invention is apvolume of liquid introduced into the vessel, the

plicable to maintaining a substantially constant liquid level drops. Conversely, it functions to relevel of liquid in scrubber, cooler and other apstore the liquid level to the predetermined posiparatus involving the introduction of gas and tion by increasing the discharge opening and corliquid or liquid alone into a vessel and discharge respondingly increasing the amount of liquid disof the same therefrom, variations in the rate of charged when the liquid within the vessel rises. 10

feed into and operating conditions within the The control preferably involves a weigh bottle vessel causing fluctuations in the level of liquid responsive to changes in liquid level within the within the vessel above and below a predetervessel, the weigh bottle being suspended from one mined point. The control constituting the presend of a balance beam. Variations of liquid level ent invention has been found in practice to be adin the vessel cause corresponding variations of 15 mirably adapted to maintaining a substantially evel in t ott o s q y increasing constant liquid level in apparatus under pressure diminishing the efiective weight of the bottle and such for example as the intercoolers, scrubbers thus rocking the end of the beam next the bottle and separators utilized in the synthesis of ameither downwardly 0' pw y- The v e t 2O monia. of the balance beam controls the operation of a One object of this invention is to provide conr y Which in turn governs the Operation of a trol apparatus having an element, sensitive to motor capable of exerting necessary f c s r changes in liquid level in a vessel, actuating a reoperating the valve in the discharge line from the lay which in turn governs the operation of a vessel. Restoring mechanism, in accordance motor capable of exerting the necessary forces with this invention, is associated with the motor against the pressure within the vessel to open or and ay for preventing Over-travel 0f the ve close a valve in the discharge line from the vessel. in the dischar e e m t e V s el a d else to Thus the rate of discharge from the vessel is DreVeht hunting Within e y e Cont ol increased or decreased depending on whether the esp v element, the Weigh bottle in the P is returned to the predetermined point. Another t d, iS Sensitive to Slight Changes in level t object is to provide such control apparatus of in the vessel and throug t relay gOVerhS the compact and simple design so as to minimize the Operation of the Se v erfloor space occupied thereby, render the parts In the accompanying drawings forming a P readily accessible and permit the efiicient operaof s Specification and showing for pu p of 5 tion thereof. Still another object is toprovide eXemplifieatiOh a Preferred form f t s vena control device of general application, involving tion but without limiting the claimed invention to an element responsive to changes in conditions uc illust at ve instance:

in that which is to be controlled, a relay, a motor Fig. l is a w at d a a mat vi w pa t level rises or falls respectively and hence the level ferred embodiment of t invention, it W b 49 for affecting the control and connections between in ec O Control apparatus embedyihg the the motor and relay for preventing hunting withpresent invention;

in the control or over-travel of the control effect- Fig. 2 is a side elevation of the control appaing element. A further object is to provide an ratus showing the apparatus in assembled form; improved relay structure which while particularly Fig. 3 is an end elevation corresponding to applicable to control apparatus for scrubber and Fig. 2; other analogous apparatus, is of general applica- Fig. 4 is a fragmentary vertical section partly tion. Other objects and advantages will appear in elevation of the relay taken in a plane passing from the following detailed description. vertically through the relay housing and relay The preferred embodiment of this invention is piston, a portion of the relay needle and relay pism designed to maintain the liquid level in a vessel ton being broken away as indicated to permit 11- under pressure, and into and from which liquid is lustration of the apparatus on a somewhat larger introduced and discharged, at a predetermined scale than would be possible otherwise; point by properly positioning the valve controlling Fig. 5 is a section through the relay needle the discharge outlet from the vessel. In other taken in a plane indicated by the line 5-5 of v words, the control functions to restore the liquid Fig. 4.

; in the vessel I0.

In the preferred embodiment illustrated in the drawings, the invention is shown incorporated in control apparatus for maintaining a substantially constant level of liquid in a vessel subjected to high pressure and into and from which liquid is continuously introduced and discharged and the present description will be confined to the present illustrated embodiment of the invention in such control apparatus. It will be noted, however, that the novel features and improvements are susceptible to other applications such, for example, as

controlling the level of liquid in boilers or in control apparatus generally. Obviously,;the apparatus could be used to control flow into a vessel as well as to control flow out of a vessel. Hence, the scope of this invention is not. confined to the embodiment herein described;

V In the drawings referring to Fig. 1,13 indicates the scrubbing tower or other vessel having an inlet line I i through which liquid under pressure or a mixture of liquid and gas under pressure passes into the vessel Ill. Gas inlet line is indicated by the reference numeral 9 and the gas outlet line by the reference numeral 8. The discharge line [2 leads to the high pressure side i3 of valve l4 which controls the fiow of liquid from the vessel. Valve {4 will be hereinafter more fully described and for further disclosure of the structure of this valve, reference may be had to my application, Serial No. 484,259 filed September 25,

1930, now Patent No. 2,035,898 granted March 31, 1936, claiming this valve. Dotted line l5 in vessel Ill indicates the height of the level of. liquid it is desired to maintain in the vessel. Adapter column l6 has its top connected by tube H to the gas space in the vessel l0 and its base connected bytube. l8 to the base of the tower or vessel ill so that the level of liquid in the adapter column is the same as in vessel ID. The adapter column provides an indirect connection between weigh bottle l9 and tower or vessel i3. If desired, direct connections between weigh bottle and the gas and liquid spaces in vessel I0 may be used. The weigh bottle 19 preferably in the form of a cylinder has its top connected by flexibles 2! with the top of the adapter column l6 and its base connected by flexibles 22 with the liquid space in the column [6. Hence, the level of liquid within the weigh bottle isthe same as in the adapter column and Weigh bottle I9 is pivoted to one end of balance beam 25.

The balance beam may be fulcrumed on any suitable bearings 26 (Fig. 3). In Fig. 4 a preferred type of suspension is illustrated. This suspension consists of tensioned spring steel strips 1, one at each side of the balance beam. The bottom of each of these strips is clamped between blocks 6 and 6', which are riveted together, and.

the tops between blocks '5 and 5 which are riveted together, leaving an intermediate free flexible portion 4. Blocks 5 and 6 are suitably secured to standard 3. The free flexible portion 4 of the strip constitutes the fulcrum point 28 of the balance beam. This type of suspension is nearer frictionless than a journal bearing, a ball bearing or a knife edge bearing and consequently, is preferred. It will be understood, however, that other types of bearing may be used. Stops 27 (Fig. 3) mounted on standard 3 and extending over the top of fulcrum point 28 of the balance beam 25 limit the rocking movement of the beam in both directions. End 29 of the balance beam is provided with an adjustable counterweight 3|. Variations of liquid level in the vessel I0, it will be noted, cause corresponding variations of evel -chamber 35 above the piston 33 bears a definite ratio to thepressure in the chamber 36 beneath the piston 33, depending on the ratio between the areas of the upper and lower surfaces of the piston. Chambers 35 and 36 are supplied with pressure fluid preferably oil through inlet pipe 3'! and inlet orifice 38 respectively, both communieating with the pressure fluid supply line 39.

The inlet orifice 38 is preferably made approximately one-half the size of the outlet orifice 43 hereinafter described. A drop in pressure of the pressure fluid, oil, entering chamber 36 takes place due to its flow through the inlet orifice 38, and the drop varies as the square of the flow.

The pressure within the chamber 36 is controlled by relay needle suspended from end 29 of the balance beam. The conical pointed end 42 of the relay needle regulates the discharge through orifice 43 in the chamber 36. With the needle in a definite position with respect to the discharge orifice, in the embodiment herein disclosed, so that the discharge orifice is approximately equal to the inlet orifice, the upward and downward forces on the piston are in equilibrium and the piston 33 remains stationary at a definite point in the relay housing intermediate the top and bottom thereof. Movement of the needle 4| away from the definite position in a downward direction causes end 42 to restrict the discharge through orifice 43 causing pressure to build up in chamber 36 with a consequent upward movement of piston 33. As soon as the equilibrium between forces'above and below the piston 33 is restored, the piston stops moving. Conversely upward movement of relay needle 4| by the upward rocking of end 29 of the balance beam 25 away from the aforesaid definite position causes an increase in the escape of pressure fluid through orifice 43 with consequent decrease in pressure in chamber 36 and descent of the piston 33. The relay piston rod 34 moves in a sleeve 40 positioned within the relay housing 32.

The relay housing 32 and associated elements are shown in structural detail in Fig. 4. To permit a ready assembly of the hollow piston rod 34 and piston 33, a bolt 44 is utilized which makes threaded engagement as indicated at 46 with the interior of the hollow rod, the small end of the bolt passing through Opening 45 in piston 33, and is secured by nut 44'. A dash pct 41 is provided within the hollow piston rod to regulate the speed of movement of piston 33 and rod 34. The dash pot stem 48 has its end 48 in threaded engagement with the interior of casing 50 suitably suspended from an arm bolted or otherwise secured to a support 52 carried by the balance beam 25. Stem 48 is connected to dash pot piston 53 through ball joint 54, the ball 55 integral with or secured to rod 48 being held in position in its seat in the dash pot piston 53 by nut 56.

The base of the dash pot piston is provided with a vertical opening 51 which aligns with the vertical channel or opening 58 passing through ball 55 and the end of dash pot rod 48. Cross drill openings 59 communicate with opening 58 and with the interior of chamber 54 which preferably is filled with oil. A collar 6| brazed or otherwise secured to a long sleeve 62 concentric with the dash pot piston 48 is positioned in the neighborhood of the cross drill openings and is adapted to be moved to cover more or less of the cross drill openings and thus regulate the effective extent of openings 59. Collar 9| is moved by the long sleeve 62, the interior of the top 63 of which is in threaded engagement with threads 64 on the dash pot rod 48. A look nut 55 maintains the sleeve 92 in adjusted position. The long sleeve 92 provides an accessible means of regulating the extent of the cross drill openings 59. Increasing the extent of the cross drill openings permits an increased rate of fiow of fluid from one side of the dash pot piston to the other and consequently results in a more rapid movement of the stepped piston 33. Conversely, decreasing the extent of the cross drill openings 59 by moving the collar 5| thereover, retards the movement of the stepped piston 33.

Relay needle 4| is connected with balance beam 25 by the flexible joint 66 involving bolt 61 threaded into the interior of the top of needle 4! and engaging pin 68 integral with or secured to the balance beam. A spring 69 is confined in the housing 10 within the needle M, the spring contacting with the pin 68 and thus providing a flexible connection between the needle M and the balance beam.

As above indicated, end 42 of the needle is formed of conical configuration, the cone, when seated within the discharge orifice completely closing this orifice. Portion I2 of the needle merges into portion I4 of greater diameter which in turn merges into a portion 15 of greater diameter In practice it has been found that the usual cylindrical needle vibrates in the discharge orifice in a manner similar to an organ reed vibrating in a current of air. Vibrations of the needle introduce a disturbing influence in the operations of the control and interfere with satisfactory operation. I have found that vibration of the needle may be eliminated by providing the needle with extensions or Wings, such as are shown at I8, Figs. 4 and 5. These wings operate in a bath of oil maintained below overflow pipe 11. These wings are located as near the point of the needle as may be convenient and in the embodiment disclosed are about four inches long and project about one-quarter or three-eighths beyond the cylindrical portion of the needle. In practice, it has been found that a needle provided with the extensions or wings herein disclosed does not vibrate, the extensions or wings exerting a dampening efiect.

The orifice 43; it will be noted, consists of a member provided with a restricted opening BI, the member resting on shoulders 82 in chamber 16. A sleeve 83 extends through opening 84 in cover 85 which secures the aforementioned hearing support 40 for the piston rod 34 within the relay housing 32. The sleeve 83 extends the full length of chamber I6, has one end brazed to orifice 43 and the other end provided with a collar 86 threaded thereon and accessible from the top of the housing. Sleeve 83 permits ready removal of the orifice plate 43 for cleaning or other purposes. A similar sleeve construction may be provided in connection with orifice 38, hereinbefore described, to permit ready removal of the orifice.

Openings 8! are formed in the sleeve 83 and permit flow of oil or other pressure fluid through the orifice 43 into chamber 16 out through the drain pipe 11.

Pivoted to the body of the piston rod 34 as indicated at 9|, is one end of a floating lever 92 (Fig. 1). The other end of the floating lever 92 is pivoted as indicated by the reference numeral 90, to the top of the cam rod stem 93 hereinafter more fully described. A valve stem 94 is associated with an intermediate point on the floating lever. The stem 94 passes through a block 95 integral with or secured to the lever 92. A spring 96 is coiled about the stem 94 and has one end contacting with the block 95 and the other end bearing against head 91 of the stem 94. Collar 98 on the stem 94 contacts with block 95 when it is moved downwardly, imparting downward motion to the stem 94. A relay or pilot valve I 0| involves the usual valve housing I92 and has the valve spool I03 slidably mounted therein. Valve stem 94 is connected with spool I03 through ball joint I04.

The relay valve is formed with pressure inlet port I05, which communicates with pressure fluid supply line I 06 in turn connected with pressure fluid pipe 39. Port I01 in the valve housing communicates through pipe line I I18 with port I09 in the servo-motor III. A drain port H2 in the base of the relay valve communicates with the drain line II3 into which the drain pipe I? from the relay housing also leads. Flange H4 on the valve spool is of an extent suflicient to close the valve port I 01 as indicated in Fig. 1. Movement of the valve spool downwardly places ports I05 and I0! into communication resulting in flow of pressure fluid from pipe I06 into ports I95, I91, through pipe I08 into port I09 into the servo-motor III. Movement of the valve spool !93 in an upward direction places port Ill'I into communication with exhaust port 1 I2 and causes exhaust of pressure fluid from servo-motor III through port I09, pipe I98. ports I9! and H2 into exhaust pipe II3.

Movement of the valve spool is effected through stem 94 and the floating lever 92 which is in turn moved by the piston rod 34. Thus, when the rod 34 moves up, it rocks the floating lever 92 about the pivot point 99 and through spring 96 pulls up on stem 94, causing the stem and connected valve spool I03 to move upwardly. When the piston rod 34 descends, it causes downward rocking of lever 92 about the pivot point 99. moving stem 94 and the connected valve spool downwardly through contact of block 95 with the collar 98. As above indicated, movement of the p ston rod 34 up or down is caused by changes f l quid level in vessel I0 and weigh bottle I9 wh ch move the relay needle II to varv the pressure in chamber 35 below the piston The servo-motor III is of suflicient size to exert the necessary forces for moving the valve stem H4 in the valve l4 against the high pressure occurring in chamber I3 of the valve through which the liquid from vessel I0 flows nto the low pressure chamber II6 of the valve I4. The valve stem H4 is preferably made integral with rod 15 which extends through the low pressure chamber H6 and is suitably secured as indicated at IIB to the stepped piston H? of the servomotor. Discharge line II9 leads from the low pressure chamber II6 of the valve to a suitable point of disposal for the liquid flowing from the vessel I0.

Oil is supplied at constant pressure to the small end of the stepped piston II1 of the servo-motor through inlet port I2I and pipe I22 which communicates with the supply line 39. The oil pressure on the small end of the stepped piston functions to return the piston when oil is exhausted from the large end. Admission of pressure fluid to the large end of the servo-motor through port I09 causes the servo-motor pistons to move f o the left as viewed in Fig. 1, increasing the extent of opening of valve I4 and consequently increasing the flow through this valve. Cc-ntrariwise, the exhaust of pressure fluid from the large end of the servo-motor through port I08 permits the oil pressure on the small end of the stepped piston II I to force it to the right, diminishing the valve opening with consequent decrease in flow from vessel I0 through valve I4 into discharge line I I9.

The restoring or compensating mechanism associating the servo-motor I II with the relay to prevent over-travel of the valve and further to prevent hunting within the system, will now be described. The restoring mechanism involves a cam having a horizontal surface indicated at I26 and an upwardly inclined surface I27. The cam is secured to bracket I28 suitably fastened to stepped piston at I29 so that the bracket I28 and connected cam reciprocate with the piston ill. Guide roll I3I provided with flanges I32 (Fig. 2) between which the cam moves, provide a guide and support for the reciprocating cam I25.

A cam follower I33, carried by the cylindrical stern I34 slidably guided in housing I35 rides on the cam I25. The base of'housing I35 is provided with vertical slots I36 permitting move ment of the inclined portion I27 of the cam therethrough. A rod I 31 suitably secured to stem I34 extends therefrom and is pivoted as indicated at I38 to the cam rod stem 03. Spring l39 coiled about stem I3I contacts with the top interior of housing I35 and with the cylindrical stem I34 and functions to hold cam roller I33 carried by the stem I34 into engagement with the cam track on cam I25. Movement of the stepped piston toward the left (Fig. 1) from the position indicated occasioned by the valve spool I03 being lowered causing pressure fluid to flow through ports I05, I07 and I09 into servo-motor, causes I the cam I25 to move toward the left with a consequent elevation of stem I34, I 31 and 93 raising the floating lever 92 about pivot point 9|, restoring the valve spool I03 to its original position and thus preventing further introduction of pressure fluid into the servo motor and consequently avoiding over-travel of valve stem II 4 and hunting within the system. The con-verse of the above operations takes place when the stepped piston is moved to the right. Thus the restoring mechanism prevents over-travel of the valve stem after each impulse imparted to the weigh bottle which is in turn transmitted to the relay conrolling the operation of the servo-motor.

The valve seat and stem and the shape of the cam I25 is designed as shown in Fig. l to prevent wire drawing in the valve I4 and to insure prompt opening of the valve from closed position with gradual movement of the valve once it is opened. The valve seat is'cylindrical as indicated at MI and is provided with a conical seating portion I42, Valve stem H4 comprises a conical seating portion I 43 adapted to register wi h and seat in I42, a cylindrical closing portion M4 of substantially the same diameter as MI and arranged to seat within MI and a trunother.

cated conical portion I45 in line with and extending from the closing portion I44. Assuming the valve is in seated position, it will be noted that the high pressure within chamber I3 acts upon the stem and maintains it in seated position. When the valve stem is moved towards the left (Fig. 1) the valve remains closed due to the cylindrical portion I44 remaining within MI and thus flow through the valve is prevented until the portion I 44 is completely removed from the seat I4I. Continued movement of the stem causes cylindrical portion I44 to leave its seat I4! and permits flow through the valve. Hence, the flow through the valve upon opening same from closed position acts upon the end of cylindrical portion I 44 remote from the seat I43 and wire-drawing on the seats I42 and I43 is eliminated.

To permit prompt opening of the valve from closed position, the cam I25 is provided with the horizontal surface I23. With the valve stem H4 in seated position, cam roll I33 rests on surface I26. Initial movement of the stepped piston with a consequent movement of cam I25, causes no movement of cam stem I35 due to the fact that the cam does not cause an upward movement of the roller I33, and consequently does not restore the floating lever 02 and the valve spool I03, hence permitting continued flow of pressure fluid into the servo-motor and a rapid opening movement of the valve I4. Once the valve is opened, the position of the parts is as shown in Fig. l, cam roller I33 resting on the base of the inclined surface I21. Further movement to the left of the servo-motor piston causes the restoring mechanism to operate to prevent over-travel of the valve stem H4 and hunting within the systern as above described.

It will be noted that any motion of the relay piston 34 is followed by a corresponding motion of the servo-motor piston II! and that for each position of the relay'piston 34, there is a corresponding position of the servo-motor piston II! and consequently a corresponding extent of opening of the valve I 4.

Figs. 2 and 3 illustrate the preferred arrangement of the parts of the control mechanism of the present invention. The arrangement shown is compact, minimizes floor space, renders the parts readily accessible, permits efficient operation thereof and the transportation of the control as a unit from one place to another. The control is preferably mounted on a casting or other support I5I. Bolted or otherwise secured to one end of the support as indicated at IE2, is the servo-motor cylinder III. Extending directly in front of the casing of the cylinder III, is the valve I4, the valve stem and the servo-motor piston rod II5 being in direct line with each Mounted preferably in a straight line across the top of the servo-motor cylinder is the cam rod housing I35, the relay valve housing I82 and the relay housing 32. A standard 3 carrying the balance beam 25 also extends up from the top of the servo-motor cylinder as indicated in Fig. 3.

The assembly of parts is adapted to be enclosed by a cover I indicated in dot and dash lines (Figs. 2 and 3).

In operation, assume that all the parts are in the position indicated in Fig. l and that oil pres sure is being supplied through pressure supply line 39, and further assume that due. to variations in pressure within the vessel I0 or due to an increase in the rate of flow of liquid into the Vessel ID, the level rises to a point above the dotted line I5. The level correspondingly rises in the adapter column I6 and weigh bottle I9 causing the effective weight of the bottle to increase. This results in a downward thrust upon the end 24 of the balance beam 25 rocking it about the fulcrum 23. Hence, end 29 of the balance beam and the relay needle 4| carried thereby is moved upwardly increasing the discharge through orifice. 43 and consequently diminishing the pressure in chamber 36. Accordingly, piston 33 descends, rocking the floating lever 92 about pivot point 96, and moving the valve spool through block 95, collar 98 and stem 94 downwardly, causing port I05 to communicate with port I Hi. Pressure fluid flows through ports I05 and Ifll from the pressure supply line 39 into pipe I08, port I09 into the servo-motor HI, causing the servomotor piston II I to move towards the left and increase the opening of valve I4, hence increasing the discharge from the vessel It) to cause the level of liquid within the vessel to return to the predetermined point I5. As the stepped piston II! moves toward the left, the cam I25 moves therewith. Cam surface I21 upon movement of cam I25 causes an upward movement of the cam roller I33 on the cam rod stem I3! and 93, causing the floating lever 92 to move upwardly about pivot point SI. This returns the valve spool I03 to its closed position, preventing further flow of pressure fluid into the servo-motor.

When the level within the vessel It! falls to a point indicated by the line I5, corresponding changes of level take place in the adapter column I6 and Weigh bottle I9 which causes return of the relay needle to position shown in Fig. 1, and causes the parts of the control apparatus to be brought back into equilibrium as shown in Fig. 1.

The converse of the above operations takes place when the level within the vessel It falls to a point below that indicated by the line I5.

The invention as hereinabove described is embodied in a particular form of construction but it may be variously embodied within the scope of the following claims.

I claim:

1. Control apparatus involving a servo-motor cylinder, a relay housing, a relay valve, a housing for a cam follower, and a standard all mounted on said cylinder, a balance beam pivoted on said standard and communicably connected with said relay housing, and means for actuating said balance beam.

2. Control apparatus, comprising in combination, a pressure fluid relay including a piston, a floating lever pivoted to said piston, a valve actuated by said floating lever, a cam follower connected to said floating lever, a second valve, means for operating said second valve and a cam for actuating said cam follower associated with said means for operating said second valve.

3. Control apparatus, comprising in combination, a pressure fluid relay including a piston, a floating lever pivoted to said piston, a valve actuated by said floating lever, a cam follower connected to said floating lever, a second valve, a servo-motor for operating said second valve, the admission and discharge of pressure fluid to "and from said servo-motor being controlled by the first mentioned valve, and a cam associated with said servo-motor for actuating said cam follower.

4. Control apparatus, comprising in combination, a pressure fluid relay having a discharge orifice, a relay needle for controlling the area of said orifice, said relay including a piston, a floating lever pivoted to said piston, a relay valve housing, a valve spool in] said housing pivoted to said lever, a cam follower pivoted to said floating lever, a second valve, a servo-motor for operating said second valve, the admission and discharge of pressure fluid to and from said servo-motor being controlled by said relay valve, and a cam associated with said servo-motor for actuating said cam follower.

5. Control apparatus, comprising in combination, a valve having a valve stem, a servo-motor for operating said valve, the piston in the servomotor cylinder being in line with the said valve stem, a relay housing, a relay valve, a housing for a cam follower, and a standard, all mounted on said cylinder and, a balance beam pivoted on said standard.

6. Control apparatus, comprising in combination, a valve, a servo-motor for operating said valve, said valve being disposed in front of the servo-motor cylinder, a relay housing having a piston therein, a relay valve comprising a housing and a valve spool, a cam follower, a cam secured to the servo-motor piston rod movable thereby, extending along one side of the servomotor cylinder and arranged to contact with said follower and, a balance beam pivoted on a standard and having one end operatively connected with said relay, said standard, relay valve and relay housing being all mounted on said servomotor cylinder.

'7. Control apparatus comprising in combination, a pressure fluid relay having a discharge orifice and comprising a relay needle controlling the area of said discharge orifice, a piston, a floating lever connected to said piston and a valve arranged to be operated by said floating lever; a second valve; means for actuating the said second valve operated by said pressure fluid relay and restoring mechanism associating said actuating means with said relay and arranged to permit a rapid initial opening movement of the said second valve from closed position and. continued gradual opening movement of said second valve.

8. Control apparatus, comprising in combination, a pressure fluid relay comprising a housing having a discharge orifice, a relay needle controlling the area of said discharge orifice, a piston arranged to move in said housing upon movement of the relay needle to alter the area of said discharge orifice, a floating lever connected to and moved by said piston and a valve arranged to be operated by said floating lever.

9. Control apparatus, comprising in combination, a pressure fluid relay comprising a housing having a discharge orifice, a relay needle for controlling the area of said discharge orifice, a piston arranged to move in said housing upon movement of the relay needle to alter the area of said discharge orifice, a floating lever connected to and moved by said piston, a relay valve arranged to be operated by said floating lever and a servo-motor, said relay valve governing the admission to and discharge of pressure fluid from said servo-motor.

10. Control apparatus, comprising in combination, a pressure fluid relay comprising a housing having a discharge orifice, a relay needle for controlling the area of said discharge orifice, a piston arranged to move in said housing upon movement of the relay needle to alter the area of said discharge orifice, a floating lever connected to and moved by said piston, a relay valve arranged to be operated by said floating lever, a servo-motor, said relay valve governing the admission to and discharge of pressure fluid from said servo-motor, a cam follower connected to said floating lever and a cam for actuating said cam follower associated with said servomotor.

11'. Control apparatus, comprising in combination, a pressure fluid relay having a discharge orifice, a relay needle for controlling the area of said discharge oriflce, a piston, a floating lever connected to and moved by said piston, a relay valve arranged to be operated by said floating lever, a servo-motor, said relay valve governing the admission to and discharge of pressure fluid from said servo-motor, a cam follower connected n to said floating lever, and a cam associated with said servo-motor for actuating said cam follower.

12. Control apparatus, comprising in combination, a pressure fluid relay comprising a piston, a floating lever connected to and moved by said piston, a relay valve arranged to be operated by said floating lever, a cam follower connected to said floating lever, means actuated by said relay valve and a cam associated with said means for moving said cam follower to actuate said floating lever.

WALTER H. KNISKERN. 

